JP2012213581A - Rf coil unit, and mri apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an RF coil unit having high decoupling capacity.SOLUTION: The RF coil unit is equipped with at least one first coil element constituted only of a main loop for receiving a magnetic resonance signal and a plurality of second coil elements constituted of the main loop and the decoupling sub-loop connected to the main loop in series and, in two arbitrary combinations of the first coil element and a plurality of the second coil elements, a part of the region surrounded by one main loop and a part of the region surrounded by the other main loop, a part of the region surrounded by one main loop and a part of the region surrounded by the other sub-loop or a part of the region surrounded by one sub-loop and a part of the region surrounded by the other sub-loop are arranged so as to be overlapped with each other.

Description

  The present invention relates to an RF coil unit and an MRI apparatus.

  2. Description of the Related Art Conventionally, an MRI (Magnetic Resonance Imaging) apparatus that receives a magnetic resonance signal from a subject using an RF coil unit including a plurality of coil elements is known. This type of MRI system performs image reconstruction processing and image processing using magnetic resonance signals received simultaneously in parallel by each coil element, so that electrical and magnetic interference between each coil element is possible. It is necessary to eliminate as much as possible. That is, a decoupling technique for eliminating coupling (coupling) between the coil elements is important.

  As a technique for decoupling each coil element, a technique of overlapping a part of adjacent coil elements is effective. Further, as a method of decoupling between a pair of coil elements that are not adjacent to each other, a sub-loop for decoupling is provided separately from the main loop in each of the pair of coil elements, and each sub-element of the pair of coil elements is provided. A technique of overlapping loops is also known (for example, Patent Document 1).

JP 2008-264497 A

  On the other hand, a flexible and bendable RF coil unit is also considered so that a part of the subject can be wrapped and covered. In such an RF coil unit, even when coil elements distant from each other are arranged in a flat plate shape, they may be arranged at spatially close positions in a curved state. In this type of flexible RF coil unit, the possibility that all coil elements are mutually coupled cannot be excluded.

  The technology disclosed in Patent Document 1 and the like is to decouple a specific pair of coil elements among a plurality of coil elements constituting the RF coil unit, and the coil elements that can be decoupled are limited.

  Therefore, there is a demand for an RF coil unit with further improved decoupling performance and an MRI apparatus including the same.

  The RF coil unit according to the embodiment includes at least one first coil element including only a main loop for receiving a magnetic resonance signal, the main loop, and decoupling connected in series to the main loop. A plurality of second coil elements composed of sub-loops of the first coil element, and in any two combinations of the first coil elements and the plurality of second coil elements, in one main loop Part of the enclosed area and part of the area enclosed by the other main loop, part of the area enclosed by one main loop and part of the area enclosed by the other sub-loop, or part of the area enclosed by one sub-loop And a part of the region surrounded by the other sub-loop are arranged so as to overlap each other.

The figure which shows the structural example of an MRI apparatus. The figure which shows the connection relation of the RF coil unit in an MRI apparatus. The 1st figure which shows an example of the arrangement | positioning relationship between a subject and RF coil unit. The 2nd figure which shows an example of the arrangement | positioning relationship between a subject and RF coil unit. The figure which shows a 1st coil element and a 2nd coil element typically. The figure explaining the principle of decoupling by the overlap of a coil element. The figure which shows the 1st example (the number of coil elements is 4) of RF coil unit. The 1st figure which shows the overlapping state between arbitrary two coil elements. 2nd figure which shows the overlapping state between arbitrary two coil elements 3rd figure which shows the overlap state between arbitrary two coil elements The figure which shows the 2nd example (the number of coil elements is 5) of RF coil unit. The figure which shows the 3rd example (The number of coil elements is 4) of RF coil unit The figure which shows the structural example by which 2 rows of RF coil units are arrange | positioned. The figure which shows the structural example of RF coil unit which has flexibility. The figure which shows the example of arrangement | positioning of the preamplification unit which RF coil unit comprises. The figure which shows the internal structural example of a preamplification unit. The perspective view which shows the example of an external appearance of a preamplification unit and a composite cable. The figure which shows the other example of arrangement | positioning of a preamplification unit.

  Hereinafter, a multi-channel high-frequency signal switching device according to an embodiment and an MRI apparatus including the same will be described with reference to the accompanying drawings.

(1) Magnetic Resonance Imaging Apparatus FIG. 1 is a block diagram showing the overall configuration of a magnetic resonance imaging apparatus 1 (MRI apparatus 1) in this embodiment. As shown in FIG. 1, the magnetic resonance imaging apparatus 1 includes a cylindrical static magnetic field magnet 22 that forms a static magnetic field, and a cylindrical shim coil 24 provided with the same axis inside the static magnetic field magnet 22. And a gradient magnetic field coil 26, an RF coil 28, a control system 30, and a bed 32 on which the subject P is placed.

  Here, as an example, the X-axis, Y-axis, and Z-axis that are orthogonal to each other in the apparatus coordinate system are defined as follows. First, the static magnetic field magnet 22 and the shim coil 24 are arranged so that their axial directions are orthogonal to the vertical direction, and the axial direction of the static magnetic field magnet 22 and the shim coil 24 is the Z-axis direction. Further, it is assumed that the vertical direction is the Y-axis direction, and the bed 32 is arranged such that the normal direction of the surface for placing the top plate is the Y-axis direction.

  The control system 30 includes a static magnetic field power supply 40, a shim coil power supply 42, a gradient magnetic field power supply 44, an RF transmitter 46, an RF receiver 48, a bed driving device 50, a sequence controller 56, and a computer 58. .

  The gradient magnetic field power supply 44 includes an X-axis gradient magnetic field power supply 44x, a Y-axis gradient magnetic field power supply 44y, and a Z-axis gradient magnetic field power supply 44z. The computer 58 includes an arithmetic device 60, an input device 62, a display device 64, and a storage device 66.

  The static magnetic field magnet 22 is connected to the static magnetic field power supply 40 and forms a static magnetic field in the imaging space by the current supplied from the static magnetic field power supply 40. The shim coil 24 is connected to a shim coil power source 42 and makes the static magnetic field uniform by a current supplied from the shim coil power source 42. The static magnetic field magnet 22 is often composed of a superconducting coil, and is connected to the static magnetic field power source 40 and supplied with current when excited, but after being excited, it is disconnected. Is common. The static magnetic field magnet 22 may be formed of a permanent magnet without providing the static magnetic field power supply 40.

  The gradient magnetic field coil 26 includes an X-axis gradient magnetic field coil 26 x, a Y-axis gradient magnetic field coil 26 y, and a Z-axis gradient magnetic field coil 26 z, and is formed in a cylindrical shape inside the static magnetic field magnet 22. The X-axis gradient magnetic field coil 26x, the Y-axis gradient magnetic field coil 26y, and the Z-axis gradient magnetic field coil 26z are connected to the X-axis gradient magnetic field power source 44x, the Y-axis gradient magnetic field power source 44y, and the Z-axis gradient magnetic field power source 44z, respectively.

  The X-axis gradient magnetic field power supply 44x, the Y-axis gradient magnetic field power supply 44y, and the Z-axis gradient magnetic field power supply 44z respectively supply the X-axis gradient magnetic field coil 26x, the Y-axis gradient magnetic field coil 26y, and the Z-axis gradient magnetic field coil 26z A gradient magnetic field Gx in the axial direction, a gradient magnetic field Gy in the Y-axis direction, and a gradient magnetic field Gz in the Z-axis direction are formed in the imaging space.

  In other words, the gradient magnetic fields Gx, Gy, and Gz in the three-axis directions of the apparatus coordinate system are synthesized, and the slice direction gradient magnetic field Gss, the phase encode direction gradient magnetic field Gpe, and the readout direction (frequency encode direction) gradient magnetic field as logical axes. Each direction of Gro can be set arbitrarily. Each gradient magnetic field in the slice direction, the phase encoding direction, and the readout direction is superimposed on the static magnetic field.

  The RF transmitter 46 generates an RF pulse (RF current pulse) with a Larmor frequency for causing nuclear magnetic resonance based on the control information input from the sequence controller 56 and transmits this to the RF coil 28 for transmission. To do. The RF coil 28 includes a whole body coil (WBC) for receiving and transmitting RF pulses built in the gantry, a local coil for receiving RF pulses provided in the vicinity of the bed 32 or the subject P, and the like. is there. The transmission RF coil 28 receives an RF pulse from the RF transmitter 46 and transmits it to the subject P. The receiving RF coil 28 receives an MR signal (magnetic resonance signal) generated when the nuclear spin inside the subject P is excited by the RF pulse, and this MR signal is detected by the RF receiver 48. The

  The RF receiver 48 performs various signal processing such as pre-amplification, intermediate frequency conversion, phase detection, low-frequency amplification, and filtering on the detected MR signal, and then performs A / D (analog to digital) conversion. Then, raw data (raw data) which is digitized complex data is generated. The RF receiver 48 inputs the generated raw data of the MR signal to the sequence controller 56.

  The arithmetic unit 60 performs system control of the entire magnetic resonance imaging apparatus 1.

  The sequence controller 56 stores control information necessary for driving the gradient magnetic field power supply 44, the RF transmitter 46, and the RF receiver 48 in accordance with a command from the arithmetic device 60. The control information here is, for example, sequence information describing operation control information such as the intensity, application time, and application timing of the pulse current to be applied to the gradient magnetic field power supply 44.

  The sequence controller 56 drives the gradient magnetic field power supply 44, the RF transmitter 46, and the RF receiver 48 according to the stored predetermined sequence, thereby causing the X axis gradient magnetic field Gx, the Y axis gradient magnetic field Gy, the Z axis gradient magnetic field Gz, and the RF. Generate a pulse. Further, the sequence controller 56 receives the raw data (raw data) of the MR signal input from the RF receiver 48 and inputs this to the arithmetic device 60.

  FIG. 2 shows an example of a detailed configuration of the RF coil 28. As shown in the figure, the RF coil 28 includes a cylindrical whole body coil 28 a (shown as a thick square frame in the figure) and the RF coil unit 100. The whole body coil 28a can be used as either a coil for transmitting RF pulses or a coil for receiving MR signals. The RF coil unit 100 is disposed in the vicinity of the subject P. For example, as shown in FIG. 2, the RF coil unit 100 is disposed on the body surface side or the back surface side, and is also disposed on the head or wrist. The RF coil unit 100 includes a large number of coil elements 101. Each coil element 101 is used as a coil for receiving a magnetic resonance signal (MR signal). Details of the RF coil unit 100 will be described later.

  The RF receiver 48 includes a duplexer 74, a plurality of amplifiers 76, a multi-channel high-frequency signal switching device 78, and a plurality of reception system circuits 80. The input side of the multi-channel high-frequency signal switching device 78 is connected to each coil element 101 and the whole body coil 28a via a connector. Each reception system circuit 80 is individually connected to the output side of the multi-channel high-frequency signal switching device 78.

  The duplexer 74 applies an RF pulse transmitted from the RF transmitter 46 to the whole body coil 28a. Further, the duplexer 74 inputs the MR signal received by the whole body coil 28 a to the amplifier 76, and this MR signal is amplified by the amplifier 76 and given to the input side of the multi-channel high-frequency signal switching device 78. The MR signals received by the coil elements 101 are amplified by the corresponding amplifiers 76 and applied to the input side of the multi-channel high-frequency signal switching device 78.

  The multi-channel high-frequency signal switching device 78 switches MR signals detected from the coil elements 101 and the whole body coil 28a according to the number of the reception system circuits 80, and outputs the MR signals to the corresponding reception system circuits 80. In this manner, the magnetic resonance imaging apparatus 1 forms sensitivity distributions according to the imaging region using the whole body coil 28a and the desired number of coil elements 101, and receives MR signals from various imaging regions.

(2) RF Coil Unit FIG. 3 is a conceptual diagram of the RF coil unit 100 provided on the body surface side and the back surface side of the subject P. In the example of the RF coil unit 100 shown in FIG. 3, four coil elements 101 are arranged in a line along the body length axis of the subject P.

  On the other hand, FIG. 4 shows an example in which two RF coil units 100 that are the same as those in FIG. 3 are arranged in parallel. As will be described later, in the RF coil unit 100 according to the present embodiment, a first coil element 101a consisting only of a main loop and a second coil element 101b consisting of a main loop and a sub-loop are mixed. However, in FIG. 3 and FIG. 4, the sub-loop portion is omitted.

  In the example of the RF coil unit 100 shown in FIGS. 3 and 4, the number of coil elements 101 arranged in a row is four, but the number of coil elements 101 is not limited to four. Further, the RF coil unit 100 shown in FIGS. 3 and 4 has a substantially flat plate shape along the longitudinal axis, but the shape of the RF coil unit 100 is not limited to a flat plate shape, and has flexibility. The sheet-like RF coil unit 100 may be curved so as to follow the shape of the imaging region of the subject (for example, the head, legs, wrist, etc.).

  FIG. 5 is a diagram schematically showing two types of coil elements 101 used in the RF coil unit 100 according to the present embodiment. The left diagram in FIG. 5 shows the first coil element 101a composed only of the main loop for receiving the magnetic resonance signal, and the right diagram in FIG. 5 shows the second coil composed of the main loop and the sub-loop. It is a figure which shows the coil element 101b. The main loops of the first and second coil elements 101a and 101b are intended to receive MR signals from the subject. On the other hand, the secondary loop in the second coil element 101 b is a loop intended for decoupling between the coil elements 101. As shown in the right diagram of FIG. 5, the secondary loop extends outward from a part of the main loop, and the secondary loop and the main loop are connected in series.

  When the RF coil units are arranged in a line array or a plane array using a plurality of coil elements, electromagnetic coupling, that is, coupling may occur between the coil elements. When coupling occurs between coil elements, various undesirable events such as SN degradation occur. Therefore, decoupling between coil elements is one of the important technical problems in the RF coil unit.

  The RF coil unit 100 according to the present embodiment includes at least one first coil element 101a and a plurality of second coil elements 101b, and further includes the first coil element 101a and the plurality of second coils. In any two combinations of the elements 101b, a part of a region surrounded by one main loop and a part of a region surrounded by the other main loop, a part of a region surrounded by one main loop, and the other sub-loop A part of the surrounding area, or a part of the area surrounded by one sub-loop and a part of the area surrounded by the other sub-loop are necessarily arranged so as to overlap each other. With this configuration, good decoupling performance is realized between all the coil elements 101.

  Decoupling between the two coil elements 101 can be realized by overlapping a part of the region surrounded by each coil element 101. FIG. 6 is a diagram for conceptually explaining this operation principle.

  FIG. 6A shows a case where the coil element (A) and the coil element (B) are adjacent to each other. In this case, the main loops can be overlapped. Assuming that current (high-frequency current) flows only through the coil element (A), if the induced current flowing through the coil element (B) becomes zero, the coil element (A) and the coil element (B) are completely Will be decoupled. As shown in the lower part of FIG. 6A, a magnetic field is generated by the current flowing through the coil element (A), and a part of the magnetic field is directed to the coil element (B). (Magnetic flux density) The direction of the magnetic field is reversed between the Bde-couple and the magnetic field Bcouple in a non-overlapping region. Therefore, by adjusting the area of the region where the two coil elements overlap, it is possible to reduce the sum (magnetic flux) of the magnetic fields interlinked with the coil element (B). As a result, the induced current flowing through the coil element (B) can be made zero, and the coil element (A) and the coil element (B) can be decoupled.

  On the other hand, FIG. 6B shows a case where the coil element (A) and the coil element (B) are not adjacent (separated). In this case, the main loops cannot be overlapped with each other, but by providing a sub loop in the coil element (A), the sub loop of the coil element (A) overlaps with a part of the main loop of the coil element (B). An area can be secured. Among the magnetic fields interlinking with the coil element (B), the magnetic field Bcouple in the region not overlapping with the interlinkage magnetic field Bde-couple in the overlapping region is opposite in the same manner as in FIG. In this case, the coil element (A) and the coil element (B) can be decoupled by adjusting the area of the secondary loop.

  Although not shown in particular, when both the coil element (A) and the coil element (B) have sub-loops, the coil element (A) and the coil element can be operated according to the same principle by overlapping the sub-loops. (B) can be decoupled.

  FIG. 7 is a diagram illustrating an example of an RF coil unit 100 in which four coil elements (1) to (4) are arranged in a row. In this example, the central two coil elements (2) and (3) are the first coil elements 101a having only the main loop, and the coil elements (1) and (4) at both ends are the main loop and the sub-loop. It is the 2nd coil element 101b which has. Further, in this example, all of the coil elements (1) to (4) are overlapped at the center of the RF coil unit 100. The overlapping region is set so as to include a predetermined same region at the center of the RF coil unit 100.

  8 to 10 are diagrams showing a specific decoupling realization state of the RF coil unit 100 shown in FIG. The decoupling between the coil element (1) and the coil element (2) can be realized by adjusting the area of the overlapping region (12) between the two (FIG. 8 (a)). The decoupling between the coil element (1) and the coil element (3) can be realized by adjusting the area of the overlapping region (13) between the two (FIG. 8 (b)). The decoupling between the coil element (1) and the coil element (4) can be realized by adjusting the area of the overlapping region (14) between the two (FIG. 9 (a)). The decoupling between the coil element (2) and the coil element (3) can be realized by adjusting the area of the overlapping region (23) between them (FIG. 9B). The decoupling between the coil element (2) and the coil element (4) can be realized by adjusting the area of the overlapping region (24) between the two (FIG. 10 (a)). And decoupling between a coil element (3) and a coil element (4) is realizable by adjusting the area of both overlap area | regions (34) (FIG.10 (b)).

  Thus, in any two combinations of the coil elements (1) to (4), that is, in all of the two combinations, the main loops, the sub-loops, or the main loop and the sub-loops always overlap each other. As a result, all of the coil elements (1) to (4) can be decoupled.

  In the configuration example shown in FIG. 7, two first coil elements 101a are arranged in the center, and all of the outer coil elements 101 (two in this example) are arranged with second coil elements 101b. Yes. Then, all the sub-loops of the outer second coil element 101b are concentrated in the overlapping region of the two central main loops. Even if the total number of coil elements 101 is 4 or more, the same configuration can be adopted as long as the total number is an even number.

  FIG. 11 is a diagram illustrating an example of an RF coil unit 100 in which five coil elements (1) to (5) are arranged in a row. In this example, the center coil element (3) is the first coil element 101a having only the main loop, and the coil elements (1), (2), (4), (5) other than the center are the main loop. It is the 2nd coil element 101b which has a subloop. In the RF coil unit 100 shown in FIG. 11, all the sub-loops of the other coil elements (1), (2), (4), and (5) are arranged at the approximate center of the main loop of the coil element (3) at the center. Are configured to overlap. Even if the total number of coil elements 101 is 5 or more, the same configuration can be adopted as long as the total number is an odd number.

  Also in the configuration shown in FIG. 11, in any two combinations of the coil elements (1) to (5), the main loops, the sub-loops, or the main loop and the sub-loops always overlap. The coil element (1) to the coil element (5) can be decoupled.

  7 and 11, the sub-loops are intensively overlapped at the center of the RF coil unit 100, but the position where the sub-loops are intensively overlapped may be other than the center of the RF coil unit 100. For example, as shown in FIG. 12, the position where the sub-loops overlap intensively may be set to a position shifted to the left instead of the center of the RF coil unit 100. In the configuration example shown in FIG. 12, the total number of coil elements 101 may be an even number or an odd number.

  Also in the configuration shown in FIG. 12, in any two combinations of the coil elements (1) to (4), the main loops, the sub-loops, or the main loop and the sub-loops always overlap. The coil element (1) to the coil element (4) can be decoupled.

  FIG. 13 is a diagram showing a multi-RF coil unit 200 configured by arranging a plurality (two in the illustrated example) of RF coil units 100a obtained by adding local coils 102 to the RF coil unit 100 shown in FIG. The local coil 102 is disposed in a region where the coil elements 101 are intensively overlapped in the central portion of the RF coil unit 100a. And the local coil 102 of each RF coil unit 100a is electrically connected by the track | line 103. FIG. The line 103 may be a coaxial cable, a parallel line, or a twisted pair line. In this multi-RF coil unit 200, since the overlapping regions in each RF coil unit 100a are coupled by the local coil 102 and the line 103, a part of each coil element 101 of the two RF coil units 100a is equivalently All of them overlap each other, and it becomes possible to decouple all the coil elements 101 in the two RF coil units 100a.

  Further, the number of turns of each local coil 102 is not limited to 1, and may be a plurality of turns. By adjusting the number of turns of the plurality of local coils 102, even if the physical area of the overlapping region in each RF coil unit 100a is small, the equivalent area of the overlapping region can be adjusted. Decoupling between 101 can be realized.

  Up to this point, the entire RF coil unit 100 has been described as having a flat plate shape, but the shape of the RF coil unit 100 is not limited to a flat plate shape. By making the RF coil unit 100 into a flexible sheet-like unit, the RF coil unit 100 is flexibly bent so that the imaging site such as the head, legs, and wrist of the subject is along the curved surface portion. And can be covered.

  FIG. 14 is a diagram illustrating an example of the RF coil unit 300 having such flexibility. 14A is a developed perspective view of the RF coil unit 300, FIG. 14B is a perspective view of the RF coil unit 300 curved along the subject, and FIG. 14C is a plan view thereof. is there. 14 (d) and 14 (e) correspond to FIGS. 14 (a) and 14 (b), respectively, and show the positional relationship of the coil elements 101 inside the RF coil unit 300. FIG. It is.

  The RF coil unit 300 includes a unit main body 301, a preamplification unit 302, and a holding member 303. The unit main body 301 includes the above-described plurality of coil elements 101 and is a flexible sheet-like unit. The holding member 303 is a belt-like member having flexibility. By attaching both ends of the holding member 303 and both ends of the unit main body 301 with, for example, Velcro (registered trademark) or the like, the unit main body 301 can be fixed in a curved state along the subject.

  Also in the RF coil unit 300, as shown in FIG. 14E, in any two combinations of the coil elements, the main loops, the sub-loops, or the main loop and the sub-loops always overlap. Thus, all the coil elements 101 can be decoupled.

  The preamplification unit 302 connects each coil element 101 and the outside by a composite cable 302a. The preamplification unit 302 is not limited to the flexible or curved RF coil unit 300 shown in FIGS. 14 (a) to 14 (e). It can be mounted on all the RF coil units 100 and 200 according to this embodiment shown in FIG. 15 to 18 are diagrams showing a more specific arrangement, configuration, and the like of the preamplification unit 302. FIG.

  The RF coil unit 100 shown in the upper part of FIG. 15 is the same as that shown in FIG. 7. In any two combinations of the coil elements (1) to (4), that is, in all of the two combinations, the main loops The sub-loops or the main loop and the sub-loop are always overlapped. The central two coil elements (2) and (3) are the first coil element 101a having only the main loop, and the coil elements (1) and (4) at both ends are the second coil elements having the main loop and the sub-loop. Coil element 101b. In the present embodiment, all of the coil elements (1) to (4) overlap each other in a region including the same region at one central portion of the RF coil unit 100.

  On the other hand, as shown in the lower part of FIG. 15, each loop of the coil element (1) to the coil element (4) is connected to the preamplification unit 302 in the same overlapping region.

  FIG. 16 is a diagram illustrating an internal configuration example of the preamplifier unit 302. The preamplifier unit 302 has a configuration in which a protection circuit 400, a balun 401, and a preamplifier 402 are connected in order corresponding to each of the coil elements (1) to (4). The protection circuit 400 is a circuit that protects the preamplifier 402 by turning on and off a PIN diode or the like in accordance with a protection circuit control signal from the outside to prevent a large amount of power during RF transmission, for example. The balun 401 is a balanced / unbalanced conversion circuit, and suppresses unbalanced current (common mode noise) generated by the connection between the coil element (balanced circuit) and the preamplifier (unbalanced circuit).

  The preamplifier 402 amplifies the magnetic resonance signals received by the coil elements (1) to (4) with low noise, and outputs the amplified signals to the outside through a coaxial cable or the like. Each preamplifier 402 is supplied with power from the outside via a power line. In FIG. 16, the preamplifier 402 is connected to the coil element (1) to the coil element (4). However, the present invention is not limited to this, and the number of the preamplifiers 402 can be changed as appropriate. Can be done.

  FIG. 16 is a perspective view schematically showing the arrangement of the preamplifier unit 302. As shown in FIG. 16, the preamplification unit 302 of this embodiment is arranged so as to overlap an area including one identical area in the center of the RF coil unit 100. Coaxial cables that output magnetic resonance signals (four coaxial cables in this example), power supply lines, protection circuit control signals, etc. are combined into one composite cable and connected to an external connector of the preamplifier unit 302. Connected.

  As described above, in the RF coil unit 100 according to the present embodiment, an electronic circuit such as the preamplifier 402 connected to the coil element (1) to the coil element (4) is included in one package (preamplifier unit 302). In the preamplification unit 302, each preamplifier 402 is connected at a position very close to all the coil elements (1) to (4). Yes. Such a configuration of the preamplification unit 302 has the RF coil unit 100 of the present embodiment in which all the loops of the coil elements (1) to (4) have a common region that overlaps at one place. It is possible depending on the characteristics.

  In the conventional RF coil unit, even if a part of each coil element overlaps, the overlapping region is not concentrated in one place but is dispersed in the RF coil unit.

  For this reason, when all the plurality of preamplifiers connected to each coil element are to be accommodated in one package, all RF feed lines (RF signal lines connecting the coil elements and the preamplifier) are minimized. It is impossible to connect at a distance. For this reason, some of the RF feeders become long. When the RF feed line is long, it is easy to receive external noise on the path from the coil element to the preamplifier. In addition, since the transmission loss of the RF feeder line increases, the noise figure increases and the SNR of the magnetic resonance signal decreases. In addition, since a part of the RF feed line that has become longer may pass through the loop surface of the coil element depending on the routing, the original RF characteristics of the coil element may be impaired.

  On the other hand, a plurality of preamplifiers connected to each coil element are not housed in one package, but are divided into a plurality of preamplifier units, and one preamplifier is provided in one preamplifier unit. A configuration for storage is also conceivable. By arranging the divided preamplifier units close to each coil element, the RF feed line connecting the coil element and the preamplifier can be shortened. However, this configuration increases the cost because the number of preamplification units increases. In addition, a composite cable including a coaxial cable or the like is drawn out from each preamplifier unit. When the number of composite cables increases, not only the handling of them becomes complicated, but also a part of the composite cables may pass through the loop surface of the coil element. The characteristics will be impaired.

  On the other hand, as described above, the RF coil unit 100 according to this embodiment includes one electronic circuit such as the preamplifier 402 connected to each of the coil elements (1) to (4). Are housed in one package (preamplification unit 302), and in this preamplification unit 302, each preamplifier 402 is connected to all the coil elements (1) to (4). It is connected at a position close to. For this reason, it is possible to make all the RF feed lines as short as possible and hardly receive external noise. Further, since the transmission loss of the RF feeder line is small, the noise figure is not lowered and the SNR of the magnetic resonance signal is not lowered. Further, since each of the coil elements (1) to (4) is substantially directly connected to the preamplifier unit 302, an RF feed line outside the preamplifier unit 302 is not necessary, and the RF feed line is a coil. It is possible to prevent deterioration of the RF characteristics of the coil element due to passing through the loop surface of the element.

  Furthermore, since the preamplifier unit 302 can be configured as one package, the number of composite cables drawn from the preamplifier unit 302 is also one. As a result, not only can the cost of the RF coil unit 100 be kept low, but the handling of the composite cable is facilitated, and the RF of the coil element due to a portion of the composite cable passing through the loop surface of the coil element. It is also possible to prevent characteristic deterioration.

  The location of the preamplifier unit 302 varies depending on the position of the common region where the coil elements overlap. For example, the figure shown in the upper part of FIG. 18 is the same as FIG. 12, but in this example, the position of the common region where the coil elements overlap is not the center but a position deviated to the left from the center. In this case, the pre-amplification unit 302 is disposed at a position biased to the left as shown in FIG. 18, but the same effect as that of the RF coil unit 100 described above can be obtained.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 MRI apparatus 100, 200, 300 RF coil unit 101 Coil element 101a 1st coil element 101b 2nd coil element 102 Local coil 103 Line 302 Preamplifier unit 303 Holding member 402 Preamplifier

Claims (15)

At least one first coil element comprising only a main loop for receiving a magnetic resonance signal;
A plurality of second coil elements composed of the main loop and a decoupling sub-loop connected in series to the main loop;
With
In any two combinations of the first coil element and the plurality of second coil elements, a part of a region surrounded by one main loop, a part of a region surrounded by the other main loop, one main Arranged so that part of the area enclosed by the loop and part of the area enclosed by the other sub-loop, or part of the area enclosed by one sub-loop and part of the area enclosed by the other sub-loop overlap. The
An RF coil unit characterized by that. The overlapping region in the two arbitrary combinations is a magnetic field that intersects the other first or second coil element among the magnetic fields generated when a current flows through one first or second coil element. Is set to reduce,
The RF coil unit according to claim 1. The first coil elements and the plurality of second coil elements are arranged in one row.
The RF coil unit according to claim 1. The total number of the first coil elements and the plurality of second coil elements is 4 or more.
The RF coil unit according to claim 3. The first coil element includes a part of a region surrounded by the main loop and a part of a region surrounded by the main loop of the other first or second coil element, or a part of a region surrounded by the main loop and the other. A portion of the region surrounded by the sub-loop of the second coil element of
The RF coil unit according to claim 4. Between the adjacent first or second coil elements, the second coil element is a part of a region surrounded by the main loop and one of the regions surrounded by the main loop of the other first or second coil element. , A part of the region surrounded by the main loop and a part of the region surrounded by the sub-loop of the other second coil element, or a part of the region surrounded by the sub-loop and the sub-loop of the other second coil element It is arranged to overlap with a part of the area surrounded by
The RF coil unit according to claim 4. In the second coil element, between the first and second coil elements that are not adjacent to each other, a part of the region surrounded by the sub-loop and one of the regions surrounded by the main loop of the other first or second coil element. Or a part of the region surrounded by the sub-loop of the second coil element and a part of the region surrounded by the sub-loop of the other second coil element,
The RF coil unit according to claim 4. In any two combinations of the plurality of second coil elements, a region where one sub-loop and the other sub-loop overlap is set to include a predetermined same region in any combination.
The RF coil unit according to claim 6 or 7, wherein The predetermined identical region is set in a main loop of the first coil element;
The RF coil unit according to claim 8. The first coil elements and the plurality of second coil elements are arranged in a row,
The RF coil unit is formed into a flexible sheet,
2. The RF coil unit according to claim 1, further comprising a holding member that holds the curved shape of the sheet-like RF coil unit in a state of being curved along the subject. A plurality of RF coil units according to claim 8, and in any two combinations of the RF coil units, a first local loop provided in a region overlapping with the predetermined same region of one RF coil unit; An RF comprising: a second local loop provided in an area overlapping with the predetermined same area of the other RF coil unit; and a line coupling the first and second local loops. Coil unit. An MRI apparatus comprising the RF coil unit according to any one of claims 1 to 11. At least one preamplifier connected to the at least one first coil element and the plurality of second coil elements and respectively amplifying a magnetic resonance signal received by the first and second coil elements; Further comprising a preamplification unit,
The preamplification unit is disposed so as to overlap the region including the overlapping region.
The RF coil unit according to claim 1. At least one preamplifier connected to the at least one first coil element and the plurality of second coil elements and respectively amplifying a magnetic resonance signal received by the first and second coil elements; One preamplification unit
The at least one first coil element and the plurality of second coil elements overlap in a region including one identical region;
The one preamplification unit is arranged so as to overlap with the region including the same region in one place.
The RF coil unit according to claim 1. A plurality of RF signals respectively output from the plurality of preamplifiers and a plurality of power supply lines for supplying power to the plurality of preamplifiers are bundled into one composite cable and are externally connected from the preamplification unit Output,
The RF coil unit according to claim 13 or 14, characterized in that

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